Skin pH and Urban Legends: An Argument Against Wait Times and pH-Adjusting Toners

Although I did listen to way too much The Who in high school, my blog is actually named after skin’s natural acidity. When left to its own devices, our skin’s pH varies quite a bit – from about 4.0 to about 5.5 – but will always fall on the acidic side of the pH scale.

(Quick refresher: the pH scale runs from 0-14. The closer to 0, the more acidic; the closer to 14, the more basic/alkaline. 7 is neutral.)

There’s one other major discussion around acidity when it comes to skincare: certain actives (specifically AHAs, BHAs, and L-ascorbic acid based vitamin C serums) require a specific pH to do their best work that’s even lower than our skin’s pH.

BHA: ideally around pH 3.0; pretty much neutralized above 4.0

AHA: ideally between pH 3.0-4.0; pretty much neutralized above 4.5

Vitamin C: ideally between 2.5-3.5; very unstable above 3.5 (only applies to formulations with L-ascorbic acid as the source of vitamin C)

These are pH-dependent actives – I’ll call them pHDAs since I’ll refer to them a lot. These are different from actives that don’t need a narrow, specific low pH – actives like retinoids and benzoyl peroxide.

pHDAs are tricky to work into our routines. How will the pH of the product interact with the pH of our faces? If we apply them to skin with a high pH, will that affect the efficacy of the product? Especially since there’s no way to measure your skin’s pH at home, there’s a lot of guessing involved. There are two popular techniques that have cropped up to theoretically optimize the efficacy of pHDAs:

Wait 20 minutes after cleansing before using pHDA to let your skin’s pH “reset” to its natural acidity

Apply a pH-adjusting toner (a simple, non-hydrating toner with a pH around 3.5-4.5) after cleansing but before pHDAs to get your skin’s pH lower than normal

After a lot of research, I’m just going to come out and say it: I think both of those are unnecessary. Here’s why.

The “Wait 20 Minutes After Cleansing” Myth

This myth is easy to clear up: according to every study I’ve read, it actually takes at least 90-120 minutes after cleansing for your skin to return to its normal pH, and possibly up to 6 hours. Check out this chart of skin pH after cleansing (the dotted line used high-pH soap, the solid line used low-pH synthetic cleanser):

So we’ve debunked the idea that it takes 20 minutes after cleansing to return to a normal pH. But more importantly, you shouldn’t have to wait for your skin’s pH to lower because you shouldn’t be raising it when you cleanse. I believe very strongly that while low pH isn’t everything when it comes to cleansers, it’s still the most important thing. Not every low-pH cleanser is good for your skin, but no high-pH cleanser is.

Why do we only talk about cleansers when we talk about pH? Every product you use should be less than 7, but because soap is naturally alkaline (around pH 10), cleansing is the step that’s most likely to screw your pH up. I’m hardly the first to wax poetic about the importance of low-pH cleansers, but here are a few reasons why you should ditch the high-pH suds.

Pathogens like P. acnes, the bacteria that causes acne, thrive at higher pHs but struggle to survive around pH 5 – one of the many reasons why your skin chose that pH in the first place. In fact, your blood is naturally slightly alkaline, so the pathogens that would do well in a basic environment like your internal organs must first cross your acidic skin, where they’ll probably die. Our bodies are fucking brilliant, man.

Conversely, there’s a lot of good bacteria that lives on your skin and helps it stay healthy, and all of those guys thrive in an acidic environment.

More recent studies have shown that several enzymes that help produce key factors in your skin’s barrier – namely, ceramides and free fatty acids – function best in an acidic environment. When your skin’s pH is too high, those enzymes don’t work as well and your skin’s barrier function starts to melt down.

A famous study gave half its participants a normal, high-pH soap cleanser and the other half a low-pH synthetic cleanser. The high-pHers saw an increase in acne lesions and the low-pHers saw a decrease – but those effects only started surfacing after 4 weeks. Raising the pH of your skin isn’t an instantaneous trauma; it’s something that builds over time to slowly break down your skin’s barrier and let in the bad stuff.

With all that data backing it up, I honestly see no reason to stick with a high-pH cleanser unless specifically advised by a doctor. Many people don’t see an immediate problem with their high-pH cleanser and assume it’s fine, but the issues with high pH are more chronic than acute and can take a while to surface.

Getting back to the point of this article, while a high-pH cleanser will significantly raise your skin’s pH for at least 90 minutes, a low-pH cleanser will only slightly raise or potentially even lower your skin’s pH. With a low-pH cleanser, there’s absolutely no need for a wait time between cleansing and applying pHDAs.

Note: my stance against wait times just applies to time between cleansing and applying pHDAs. I still believe in wait times after applying pHDAs, to give them some time at their lower pH to do their stuff.

You Probably Don’t Need a pH-Adjusting Toner

Let’s assume, for the sake of argument, that we’re all using a low-pH cleanser at this point, so we’ve washed our faces and our skin is now around pH 5.0. (Our skin’s pH varies pretty wildly throughout the day and from person to person, so this is just a total ballpark.)

Some would argue that a pH-adjusting toner – a non-hydrating toner that’s just there to lower your skin’s pH to, say, 4.0 – is an ideal next step. In theory, since pHDAs need those lower pH ranges I listed above, then wouldn’t your skin with its pH of 5 raise those pHDAs out of their effective zones? Or, put another way, wouldn’t a pHDA that thrives in low pH do better on skin that’s 4.0 than 5.0?

I want to preface this by saying I’m not a chemist and this is just based on my own research and intuition, but: nah. The thing is, when scientists worked out what the effective ranges of various pHDAs are, they were testing them on human skin. When they applied a BHA at various pHs to people’s faces and figured out that a pH of 3.0 worked best, they did that on human skin.

(If you want to know more about how pH affects the efficacy of AHAs and BHAs, read this post.)

For the most part, I trust cosmetic chemists. They know what they’re doing. They’ve formulated these pHDAs at these pHs because that’s ideal for use on bare skin with bare skin’s regular pH.

If you lower the pH of your skin below normal, then more of the pHDA will be in its free acid form, making it stronger than it was intended to be. I experienced this first-hand: when I used Cosrx AHA/BHA Clarifying Treatment Toner as a pH-adjusting toner, I found that the pHDAs I’d used for months with no problems were suddenly giving me red, raw, irritated skin. My pHDAs were suddenly way too strong, because less was being neutralized on my skin than was originally intended by the creators of the product.

The one exception: if there’s a pHDA that used to work for you but has started to feel less effective, adding a pH-adjusting toner beforehand can give it a boost. Other than that, I think pH-adjusting toners before pHDAs are largely overkill and can even potentially harm your skin, making pHDAs too strong and therefore causing irritation and other damage. (Of course, some people can tolerate acids better than others, so many won’t have an issue with this.)

To summarize: if you use a low-pH cleanser, your skin’s already the right pH for pH-dependent actives. You can cut it out with wait times and pH toners, if you want.

The Big Exception

To quote Holy Snails: “YMMV (Your Mileage May Vary) is the only gospel in skincare.”

If a pH-adjusting toner has worked great for you, awesome! If you’d rather wait 20 minutes after cleansing, be my guest. This is just my personal research, meant to educate and inform, not prescribe and enforce.

But if you, like me, have been trying to figure out all this conflicting advice about wait times and toners and cleansers and pHs – I hope this helps simplify the science behind it, at least.

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47 comments

I was really excited to see the title of your post today. I’m on the AB Reddit (UN is apathetichearts) and as much as I enjoy that community I feel like there’s this hive mind type thing going on as far as some subjects. Everyone tells you that you NEED a PH adjusting toner and you MUST wait. I feel like this is actually harmful for the countless new people coming in, it needlessly complicates an already must more complicated routine than they’re used to and it’s damaging to the many of them starting acids for the first time.

I think the problem for 75% of people using acids is over-exfoliation, not that their acids aren’t strong enough. Now there are many people, like myself, who are tolerant to acids and I do try to get the most out of them for that reason. But after I use up my Cosrx toner (which didn’t do much for me tbh) I think I’m just going to get a stronger BHA instead of having an additional step.

It’s supposed to be YMMV but there’s a lot of the same advice given to everyone. And it just irritates me that people read one post by a blogger and suddenly it’s fact, they blindly preach it without educating themselves or seeing if the advice they’re parroting actually works for them and their skin.

Regarding low PH cleansers though… what do you think about the study someone posted recently that washing your face raised the PH of your skin an insignificant amount regardless of what cleanser you use? I’ll see if I can find the link if you don’t know what I mean.

Thanks! For that article you mentioned, was that the blog post recently advocating high-pH cleansers? As I remember, all the research cited in that paper was actually in favor of low-pH cleansers, but the conclusion drawn was that high-pH cleansers weren’t that bad. I was…confused. I’d love to see a more thorough explanation of how he reached his conclusions.

Bahaha no, though I read that very contradictory blog post as well. I believe he did mention the same study though… and Benton made a social media post about it recently too? I don’t know why I can’t find it right now and I’m not even sure if it’s even legit, I was just curious about it. Basically they measured the PH of your skin before and after washing and the difference was minute.

I was also pretty surprised with the number of people on reddit using a pH-adjusting toner. Or maybe I’m a cheapskate who always opted to wait. Haha. Anyway, this was a great read! I’ve been testing a couple of vitamin C serums and seeing how well they play with a BHA. It also reminds me not to be so anxious about wait times, etc. that we forget about the relaxing, enjoyable part of skincare. Heading back to your BHA/AHA post now. 🙂

I’m basically way too cheap for a pH adjusting toner, which is why I don’t have one, LOL. I also just didn’t see the point (personally), especially as the acids my skin seems to like are the ones in the weak pH adjusting toners!

Yes, this!! The advice to use a pH adjusting toner never made sense to me, especially if you’re already using a low pH cleanser. It just seemed like an extra step that I didn’t need in my routine. Glad you wrote this post!

First of all thank you so much for this piece. I really feel like your posts have all been incredibly valuable and well-thought out. I really appreciate this guidance and it all intuitively makes sense to me. Do you think that a PH balancing toner (I just purchased the Acwell Licorice Toner that claims to have PH of 5.5-6 although I haven’t test it yet) would be fine and wouldn’t cause any problems with overly potentiating acids applied after?

I have a friend that experienced the same thing you did by using the Cosrx PH adjusting toner. She felt that the AHA that she was using with no issues beforehand ended up burning her skin and she had to stop using all not uber gentle products for a long while. So this is good advice and just clarifies something we had thought for awhile now.

I really enjoy reading your posts, they offer so much food for thought. My personal opinion is that the discussion about ph of products is really important because it can make a real difference. But everyone has to try what works best, also when it comes to cleansing and actives. My experience tells me that I need a ph adjusting toner after cleansing even if I’m using just a cleansing balm (no ph) or a mild cleanser with a ph around 5 – acids just work so much better. But I don’t know the normal ph of my skin, maybe it’s higher than 5,5. And I haven’t sensitive skin so it’s not very reactive. The part about the waiting time after cleansing is really interesting and I’m sure you’re right because I read something like this in a study some time ago, the skin needs much more than 20 minutes to to return to its usual ph.

I thought I had remembered reading research that said it took much longer than 20 minutes for skin to return to its optimal pH state. I’m glad I wasn’t just losing my mind! I thought it was odd that 20 minutes was the widely recommended wait time, but figured maybe I was missing something.

As for pH adjusting toner, I just recently started using one. I’ll be honest, though, I don’t really think it does much for me. My cleanser has a pretty low pH though, so I assume that’s why. I tried it more out of curiosity and science than legitimate need, haha. Story of my AB life.

Great post! I can’t entirely agree about trusting cosmetic chemists to know what they’re doing (cosmetic chemists make the high pH cleansers too, after all, and all the high pH/wash-off hydroxy acid products), but I’ve been increasingly convinced that long wait times and pH-adjustment obsessiveness are overkill (I may be partially attempting to justify my own biases too, because I don’t have the patience for an hour-long routine…). I also think the repeated wetting and drying could cause more harm than good.

Great post! I can’t entirely agree about trusting cosmetic chemists to know what they’re doing (cosmetic chemists make the high pH cleansers too, after all, and all the high pH/wash-off hydroxy acid products), but I’ve been increasingly convinced that long wait times and pH-adjustment obsessiveness are overkill (I may be partially attempting to justify my own biases too, because I don’t have the patience for an hour-long routine…). I also think the repeated wetting and drying could do more harm than good.

Not unless you have a friend who works at a lab. Since our skin has so much oil, and pH testing is figuring out the concentration of hydrogen ions in an aqueous (water) solution, it takes a lot of very complex methodology and very expensive equipment to accurately test skin’s pH. 🙁

I have read that post! It’s a great one. My feeling is that there are two kinds of pH toners you can use: one that is around your skin’s natural pH (5 or so), in which case, I think it’s unnecessary because your skin will be around there after cleansing anyway if you’re using a low-pH cleanser; or, one that’s lower than your skin’s natural pH (like the Cosrx), which will boost the strength of the pHDA you use after it – which can be a good thing or a bad thing.

Which part are you referring to? All the science-part is from peer reviewed studies (linked in the sources). The conclusions are my own, based on those studies combined with my personal analysis and experiences.

Great post. I always run the science parts by my husband, who is a biochemistry professor:) I have been trying to get him to make me an LAA serum in his lab….. (apparently it takes a lot of “time” and he has to do all this “work” etc), and now I am going to ask him to ph test my face!! And he has a colleague who is Korean who can read things like packages and ingredient lists!
Anyway, when I read the title I was excited for a minute because I thought we didn’t have to wait AFTER the actives application:( Then I was sad. But then I was happy again because I have been having some irritation after my evening routine after introducing a stronger version of p50 lotion (as a ph adjusting toner):) I thought I had to drop back down to the p50 “for mature skin”, but I will try NOT using an active after before giving up the hardcore p50…

My thought though is, since PH lowering toners are such a big part of current K Beauty, and since many of us who have embraced this multi step plan use products from Korea- it seems to me that the lowering toner works well with it’s sister K acid products in terms of strength-perhaps having been designed to do so.. I think that, like Snow White, you may have had a reaction to the Cosrx – she loves the Mizon and has no issues with it. I myself find I can use either of those with my acids without problem and I am loving the result.

I’ve used other pH lowering toners with similar results – the lower the pH, the stronger the irritation, which makes sense given that low pH = stronger acids. I agree that it might work better with weaker K-skincare acids like betaine salicylate, but that goes back to my point that the only real use of pH toners is if you don’t find your current acids strong enough. I definitely don’t think they need to be an essential part of a baseline AB routine. Whatever works for your skin, though!

I randomly came across this study (http://file.scirp.org/pdf/JCDSA20110300003_47271819.pdf). In it, they are comparing an o/w emulsion at different pH on middle-aged adults and elderly. On one of the figures, we can see that the emulsion with a pH of 5.5 increased the skins pH whereas the other ones lowered it or it remained the same. Now this leads me to believe, and I’m just speculating, that our low pH cleansers aren’t low enough. We already know that cleansing raises our skins pH, even if we’re using an acidic cleanser. But most acidic cleansers are around 5.0-5.5, so what happens if we go lower? I suspected we will see similar results as this study. I realize an emulsion is different from a cleanser, but pH is still pH regardless of its form.

Interesting! I just skimmed it but it seems to focus on elderly (80+) skin, which has a higher pH than young or middle aged skin (~6.0 in elderly vs. ~5.0 in younger). They found that low-pH products helped increase barrier function in elderly skin, which makes sense since it’s bringing the skin’s pH down to its younger level. It’s unclear if that’s necessary for younger skin that’s still around pH 5.0, though. But still a super interesting read, thanks for sharing!

Hi there! Great informative post! I would like to note there is a different reason to use a low-pH toner though, even if you use a low-pH cleanser, and that is if (like me) your tap water is super hard. My city tap water consistently clocks in at about a pH of 8 and leaves calcium deposits on everything. So I use a mild, low-pH toner to cancel out some of my more-basic-than-I’d-like rinsing water. My skin is much happier since starting this (with the Mizon AHA BHA toner), and I haven’t noticed any difference in my daily AHA/BHA strength. The CosRx toner is more acidic though. I never see this mentioned, so I hope it can help fellow hard-water sufferers!